1. Field of the Invention
The present invention generally relates to additives used in photoresist materials and, more particularly, to the use of certain base compounds as acid scavengers in chemically amplified photoresists based on poly(hydroxy styrene).
2. Background Description
Manufacturing of semiconductor devices is dependent upon the accurate replication of computer aided design (CAD) generated patterns onto the surface of a device substrate. The replication process is typically performed using lithographic processes followed by a variety of subtractive (etch) and additive (deposition) processes. Optical lithography patterning involves projecting an image of a pattern, reduced in size, onto a photosensitive film (photoresist or resist) on the device substrate. Other techniques may also be employed whereby energy (UV or light) is projected onto the photoresist to effect relative changes (chemical or physical) between the exposed and unexposed portions of the photoresist material, such that portions of the photoresist material can be selectively removed to leave a desired photoresist pattern on the substrate surface. The photoresist is therefore a critical component in the manufacture of semiconductor devices.
Chemically amplified photoresists based on poly(hydroxy styrene) (PHS) have been used in the past in the field of substrate patterning. These types of resists include a PHS polymer which is modified on at least a portion of the polymer backbone at the sites of the phenolic hydroxy moieties with an acid labile functional group, a solvent for the modified PHS polymer, and an acid generating compound dissolved in the solvent with the modified PHS polymer. Often, the PHS polymer is modified in the solvent by performing an acid catalyzed reaction with the pre-formed PHS polymer using an acid labile protecting group. The acid generating compound can be added to the mixture after modification of the PHS polymer, and should be uniformly distributed within the mixture. The photoresist is deposited on a substrate, such as a wafer or chip, by spin coating or other suitable means. Subsequently, the photoresist is patterned by selective exposure of portions of the photoresist to an energy source such as a laser. The acid generating compound will be selected based on the type of energy used for patterning (e.g., E-Beam, I-line, deep-UV, etc.). Upon exposure to the light energy (radiation), the acid generating compound will produce an acid which will, in turn, cause the acid labile functional group to be removed from the backbone of the modified PHS polymer.
Chemical amplification of photoresist materials are described in detail in U.S. Pat. No. 5,252,435 to Tani et al., U.S. Pat. No. 5,258,257 to Sinta et al., U.S. Pat. No. 5,352,564 to Takeda et al., and U.S. Pat. No. 5,210,000 to Thackeray et al., all of which are herein incorporated by reference.